1. Field of the Invention
The present invention relates to a tire vulcanizing machine, and more particularly to a breach lock mechanism in a tire vulcanizing machine.
2. Description of the Prior Art
One example of tire vulcanizing machines in the prior art is shown in FIGS. 5 to 7. In FIG. 5, an upper mold 01 and a lower mold 02 are pressurized via an upper ring 03, a lower ring 04 and an intermediate lock ring 05. The intermediate ring 05 consists of two half rings integrated by means of assembling bolts and its vertical cross-section is of E-shape as shown in FIGS. 6 and 7. An annular projection at the top end of the lower ring 04 is slidably fitted in an annular groove 07 in the intermediate lock ring 03. A lower edge 08 of the upper ring 03 is provided with notches 09 and teeth 010, and an upper edge 011 of the intermediate lock ring 05 is provided with corresponding teeth 012 and notches 013.
Accordingly, by rotating the intermediate lock ring 05 (in the direction of arrows in FIG. 7) the upper ring 03 and the lower ring 04 can be separated (in the direction of an arrow in FIG. 6) or jointed.
It is to be noted that with regard to a mold clamping device in a tire vulcanizing machine of the above-mentioned type, Japanese patent application was filed and laid open as Laid-Open Japanese Patent Specification No. 59-138432 (1984).
According to the prior art as described above, the jointing means between the upper mold 01 and the lower mold 02 consists of four pieces of an upper ring 03, a lower ring 04 and an intermediate ring 05 (divided into two halves).
Accordingly, as a result of the large number of the jointing pieces, the structure becomes complexed and a cost is raised.
Moreover, in the prior art, since a pressurizing force is applied to a central portion of an upper metal mold, during a pre-pressurizing period before vulcanization, all the pressurizing force is received by the metal mold and the metal mold bears against its reaction force at its outer circumference. Hence, bending stress in a flat plate portion of the metal mold becomes large, and so, there exists a problem that it is necessary to use a metal mold having a mechanical strength higher than that necessitated for real vulcanization.